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rubin HeadWizer Joined: Jun. 23, 2000 |  Message [#1] posted on: 10-25-2001 09:20 AM CST (US).   |  |  Here is the schematic as measured by me, so it might be wrong. If anything looks totally off, please let me know so I can change it. http://www.geocities.com/rubin_jpk/rubin/page_4.html I don't really know what the implications of these values are, but this should be the beginning of another long thread ... :) Oh yeah, I also added some of my art homework in section 2. Please give it a look! [Edited by rubin on 10-25-2001 at 05:59 PM.] |
ahall HeadWizer Joined: Jun. 25, 1999 | Message [#2] posted on: 10-25-2001 10:15 AM CST (US). | | Based on the photo, it appears that the your .465M resistors should be .464M (464K ohms). I'm not measuring though--just eyeballing. |
| Apheared HeadWizer Joined: N/A | Message [#3] posted on: 10-25-2001 11:01 AM CST (US). | | You do know you're going to hell for this, right? :P HEY! 464k. yellow blue yellow. Now we know. All the guesses re: your inital photo. There's no 122k, but there is a 121k. brown red brown. We could always see that one. And, same for the bypass cap, there's no 112nF AFAIK... but there are .1uF and .12uF. 5uF is a cap value but 4.7uF MKPs are common... if it measured 5.0uF then that's about the limit of a 5% tolerance.. probably a 5.1uF... and that looks alot like a 5.1uF Solen FastCap in size and composition. I'm guessing of course. But the damn ink rubs off so easy on Solens anyway. Here, look for yourself: www.solen.ca/pics/mkp.jpg so: Great, now I'm going to hell with you. But I guess you want that anyway... Suffering is inevitable. When we suffer alone, it is a great burden which weakens our spirits and prevents us from happiness btw, who did the measuring for ya? a headwizer? [Edited by Apheared on 10-25-2001 at 02:11 PM.] |
| rubin HeadWizer Joined: Jun. 23, 2000 | Message [#4] posted on: 10-25-2001 11:10 AM CST (US). | | Hey apheared, are you making fun of my essay? I will have use my art powers to increase your awareness! Haha. thanks for clarifying the values. I always thought those caps might be solens. BTW they measure at 4.95. Thanks to thomas, I just posted a proper schematic on my site. visit page 4 for details. [Edited by rubin on 10-25-2001 at 02:13 PM.] |
| Apheared HeadWizer Joined: N/A | Message [#5] posted on: 10-25-2001 11:13 AM CST (US). | | are you making fun hehe kinda... also just showin ya I did read it... |
| rubin HeadWizer Joined: Jun. 23, 2000 | Message [#6] posted on: 10-25-2001 11:19 AM CST (US). | | What can I say, I am a romantic and an idealist ... |
| ahall HeadWizer Joined: Jun. 25, 1999 | Message [#7] posted on: 10-25-2001 01:16 PM CST (US). | | Rubin, Please recheck the parts designation on your drawing: On the RIGHT side of the drawing you have "A" and "D". This should be changed to "D" and "C". A lists 100K and should be 464K. B lists 100K also and should be 122K. The rest of the drawing is correct (according to the NJM4546a IC pinouts). |
| ahall HeadWizer Joined: Jun. 25, 1999 | Message [#8] posted on: 10-25-2001 01:18 PM CST (US). | | Typo above: I meant NJM4556a opamp. |
| rubin HeadWizer Joined: Jun. 23, 2000 | Message [#9] posted on: 10-25-2001 01:35 PM CST (US). | | Whoops, i only changed one side... thanks, I'll correct it immediately! --- I corrected the letters as well as the values as suggested by apheared. [Edited by rubin on 10-25-2001 at 06:03 PM.] |
aos HeadWizer Joined: Jun. 15, 2008 | Message [#10] posted on: 10-26-2001 11:49 AM CST (US). | | Strange that Grado is using resistors in the hundreds of megaOhm range to set the gain. High value resistors are usually avoided in this application since they generate more noise... |
| Joobu HeadWizer Joined: N/A | Message [#11] posted on: 10-26-2001 06:55 PM CST (US). | | I think you mean kilo ohm :) A 100kOhm resistor in the audio bandwidth generates 5.5uV (rms) of noise. That's probably 2-5 times more voltage noise than the op-amp. Not really significant I feel. The use of high value resistors does reduce the power requirement and increases the drive capability to the headphones. I guess you end balancing it somehow. |
| BIG Dave Member Joined: Oct. 7, 2001 | Message [#12] posted on: 10-27-2001 06:57 AM CST (US). | | Just for the sake of comparison: CMOY: opa2134, Rb=100k, Rc = 1k, Rd= 10k, C1=0.1uF Do I have this right? What should I expect if I swaped out RC, Rd, and C1 in my CMOY with the Grado values? [Edited by BIG Dave on 10-27-2001 at 10:01 AM.] |
| Selftitled Member Joined: N/A | Message [#13] posted on: 10-27-2001 03:46 PM CST (US). | | Hey rubin great job with all of this!! i give u mad props for it :p I would just like to know if anybody has begun to build one yet |
| elvis Member Joined: N/A | Message [#14] posted on: 10-30-2001 07:20 PM CST (US). | | Looking at the pictures, it seems like the pot is not grounded. Anyone can confirm this? |
| keith birss Member Joined: N/A | Message [#15] posted on: 10-31-2001 04:17 AM CST (US). | | hi more likely yellow violet yellow which is a standard value at 470k as would red brown red be 1k2 .use first two colours for value 3rd color for multiplier and 4 th color for tolerance e.g green =.5% brown =1% red = 2% gold =5%. of course there are more than series of resistors so in case 2 you would read the first 3 for value 4 for multiplier then % so a 465k would read yellow blue yellow orange if that helps any |
| Apheared Member Joined: N/A | Message [#16] posted on: 10-31-2001 05:35 AM CST (US). | | Makes no sense. 5 bands; 3 value, 1 multiplier, 1 tolerance. So 470k would read yellow violet black orange brown... So that's not a possible value. it's 464k. I'd have said 46.4k had he not measured it @ 465k. That multiplier band looks decidedly red not orange. But whatever. None of this matters anyway. It's just a feedback resistor in a single opamp analog circuit. Just use this to set your gain in combination with the inverting input's resistor... in fact, if those are the real values listed (if this really is an RA-1 circboard, whatever) then you could do better on the matching for inputs anyway. Try 100k to 121k/680k... closer offset match and more gain. Or try 82k to 100k/470k. There's really only two things you need to watch: gain = 1+(R2/R1) and matching input impedances so Rin is equal to (Rg*Rfb)/Rg+Rfb (eg parallel) You do not NEED to copy the values verbatim. |
| ahall HeadWizer Joined: Jun. 25, 1999 | Message [#17] posted on: 10-31-2001 09:33 AM CST (US). | | A precision metal film resistor, utilzing the color banding system, can have UP TO 6 bands. However, the 6th band is not commonly used. For a Precision METAL FILM 464k Ohm resistor at 1% tolerance: Band 1 = Yellow, 1st digit http://www.goldpt.com/rstrcode.html [Edited by ahall on 10-31-2001 at 04:56 PM.] |
| rubin HeadWizer Joined: Jun. 23, 2000 | Message [#18] posted on: 11-01-2001 10:42 AM CST (US). | | elvis: The pot is grounded via the metallic spray coating the entire inside of the amp. And yes it IS a real RA-1. grum... |
| Joseph Lau HeadWizer Joined: N/A | Message [#19] posted on: 11-02-2001 12:45 AM CST (US). | | Why it need 5mfd ? It Input impedance very high ? |
| Tomo Headphone Council Joined: May 4, 1999 | Message [#20] posted on: 11-02-2001 05:34 AM CST (US). | | Hello, I know that in many cases one of important factor to choosing parts is convenience. For example, you may have the parts already or you may have a deal with manufactures. I think you people are being so restrictive about choice of parts without knowing true properties and the reasons for the compromises. You should feel free to use different parts. Perhaps they may sound a lot better. Tomo |
| rubin HeadWizer Joined: Jun. 23, 2000 | Message [#21] posted on: 11-02-2001 04:49 PM CST (US). | | Listen to Tomo. Tomo knows amps. |
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